STRATEGIES FOR PLANT-REGENERATION FROM MESOPHYLL PROTOPLASTS OF THE RECALCITRANT FRUIT AND FARMWOODLAND SPECIES PRUNUS-AVIUM L (SWEET WILD CHERRY), ROSACEAE

Large yields of viable protoplasts were isolated from mesophyll tissues of the sweet cherry (Prunus avium L.) scion varieties Early Rivers and Van 2D and the rootstock genotype Pontavium 8574 V1813, provided the antioxidant, PVP-10, was added to the enzyme mixture. Following culture, using modified MS-based media (for Early Rivers and Pontavium) or K8P medium (for Van 2D), protoplasts entered division to give at first microcallus (for all genotypes), then callus (for Early Rivers and Pontavium), with shoots being regenerated from the protoplast-derived calli of the rootstock genotype Pontavium. Addition of the antioxidants, glycine and/or PVP-10, to the culture media was a requisite for negation of phenolic browning of protoplasts and protoplast-derived tissues at all culture stages. The regenerated shoots of clone Pontavium were successfully rooted when co-cultured with shoots of another, easy-to-root cherry genotype. This is the first example of a protoplast-to-tree system for the recalcitrant species Prunus avium L.